ios - UITableViewCell 子类的行为不像 UITableViewCells

Question

我的函数接受类型为 (cell: UITableViewCell, item: AnyObject) -> () 的函数作为参数。

我的问题是，当我尝试将具有 UITableViewCell 的子类 的函数作为参数传递时，出现错误:

无法将类型“(tableCellSubclass, post: Post) -> ()”的值转换为预期的参数类型“(cell: UITableViewCell, item: AnyObject) -> ()”

如何更改类型为 (cell: UITableViewCell, item: AnyObject) -> () 的函数，以便使用 UITableViewCell 的子类的函数符合它？

这里是相关的代码片段。第一个是我要实例化的 ArrayDataSource。

class ArrayDataSource: NSObject, UITableViewDataSource {
    let items: [AnyObject]
    let cellIdentifier: String
    let configureCellBlock: (cell: UITableViewCell, item: AnyObject) -> ()

    init(items: [AnyObject], cellIdentifier: String, configureCellBlock: (cell: UITableViewCell, item: AnyObject) -> ()) {
        self.items = items
        self.cellIdentifier = cellIdentifier
        self.configureCellBlock = configureCellBlock
        super.init()
    }

    func itemAtIndexPath(indexPath: NSIndexPath) -> AnyObject {
        return items[indexPath.row]
    }

    func tableView(tableView: UITableView, numberOfRowsInSection section: Int) -> Int {
        return items.count
    }

    func tableView(tableView: UITableView, cellForRowAtIndexPath indexPath: NSIndexPath) -> UITableViewCell {
        let cell = tableView.dequeueReusableCellWithIdentifier(cellIdentifier, forIndexPath: indexPath)
        let item = self.itemAtIndexPath(indexPath)

        configureCellBlock(cell: cell, item: item)
        return cell
    }
}

这是我从中实例化 ArrayDataSource 的地方，也是我收到错误的地方。

override func viewDidLoad() {

        // ...

        let postsArrayDataSource = ArrayDataSource(items: posts, cellIdentifier: "tableCell", configureCellBlock: configurePostTableViewCell)

        // ...
}

最后，这是我想作为参数传递的函数。

func configurePostTableViewCell(cell: postTableCell, post: Post) {
        //sets up formatted string for last confirmed
        let lastConfirmed = dateSimplifier(post.confirmed)
        var boldLastConfirmed = NSMutableAttributedString()
        boldLastConfirmed = NSMutableAttributedString(string: "last confirmed: \(lastConfirmed)", attributes: [NSFontAttributeName:UIFont(name: "AvenirNext-Italic", size: 15.0)!])
        boldLastConfirmed.addAttribute(NSFontAttributeName, value: UIFont(name: "AvenirNext-DemiBoldItalic", size: 15.0)!, range: NSRange(location: 16, length: lastConfirmed.characters.count))

        //sets up formatted string for posted date
        let posted = dateSimplifier(post.posted)
        var boldPosted = NSMutableAttributedString()
        boldPosted = NSMutableAttributedString(string: "posted: \(posted)", attributes: [NSFontAttributeName:UIFont(name: "AvenirNext-Italic", size: 15.0)!])
        boldPosted.addAttribute(NSFontAttributeName, value: UIFont(name: "AvenirNext-DemiBoldItalic", size: 15.0)!, range: NSRange(location: 8, length: posted.characters.count))

        //sets up formatted string for title & type
        let title = post.title
        let type = post.type
        var boldTitle = NSMutableAttributedString()
        boldTitle = NSMutableAttributedString(string: "\(title)  \(type)", attributes: [NSFontAttributeName:UIFont(name: "AvenirNext-DemiBold", size: 18.0)!])
        boldTitle.addAttribute(NSFontAttributeName, value: UIFont(name: "BodoniSvtyTwoSCITCTT-Book", size: 18.0)!, range: NSRange(location: title.characters.count + 2, length: type.characters.count))
        if (type == "free") {
            boldTitle.addAttribute(NSForegroundColorAttributeName, value: UIColor(red: 1.0, green: 0.5, blue: 0.5, alpha: 1.0), range: NSRange(location: title.characters.count + 2, length: type.characters.count))
        } else if (type == "cheap") {
            boldTitle.addAttribute(NSForegroundColorAttributeName, value: UIColor(red: 0.0, green: 0.75, blue: 1.0, alpha: 1.0), range: NSRange(location: title.characters.count + 2, length: type.characters.count))
        }

        //sets values for strings in cells
        cell.titleLabel.attributedText = boldTitle
        cell.lastConfirmedLabel.attributedText = boldLastConfirmed
        cell.postedLabel.attributedText = boldPosted

        //sets image based on post's status
        switch post.status {
        case 0:
            cell.statusImage.image = UIImage(named: "Help Filled-50.png")
        case 1:
            cell.statusImage.image = UIImage(named: "Good Quality Filled-50.png")
        case 2:
            cell.statusImage.image = UIImage(named: "Poor Quality Filled-50.png")
        case 3:
            cell.statusImage.image = UIImage(named: "Help Filled-50.png")
        default:
            NSLog("Unknown status code for post.")
        }
  }

Answer 1

您可以使用泛型来实现这一点。创建一个通用的 ArrayDataSource:

class ArrayDataSource<T: UITableViewCell, U: AnyObject> : NSObject, UITableViewDataSource {

    let items: [U]
    let cellIdentifier: String
    let configureCellBlock: (cell: T, item: U) -> ()

    init(items: [U], cellIdentifier: String, configureCellBlock: (cell: T, item: U) -> ()) {
        self.items = items
        self.cellIdentifier = cellIdentifier
        self.configureCellBlock = configureCellBlock
        super.init()
    }

    func itemAtIndexPath(indexPath: NSIndexPath) -> U {
        return items[indexPath.row]
    }

    func tableView(tableView: UITableView, numberOfRowsInSection section: Int) -> Int {
        return items.count
    }

    func tableView(tableView: UITableView, cellForRowAtIndexPath indexPath: NSIndexPath) -> UITableViewCell {

        let cell = tableView.dequeueReusableCellWithIdentifier("identifier", forIndexPath: indexPath) as! T
        let item = self.itemAtIndexPath(indexPath)

        configureCellBlock(cell: cell, item: item)

        return cell
    }
}

像这样针对您的单元格和项目创建一个:

let postArrayDataSource = ArrayDataSource<postTableCell, Post>(items: posts, cellIdentifier: "tableCell", configureCellBlock: configurePostTableViewCell)